Started work this morning on mt E720, since my parts unit came in the mail the other day. I typically don't document anything I do, but since it's a "rare" model....
The armature was dated 1923. Unit one had a bum armature, but the unit two armature looked like it was new after lots of cleanup. These things have zinc bushings, and they swell and seize. Trust me, no amount of oil will help it. I normally lap the bushing with some valve compound and an old armature, but was lazy and used my aluminum polishing compound to do the same thing. Here's the offending bushing (one of them anyhow), with the fields gutted out of it.
The motors on these things should zip up, and sound like any other upright, and not sound labored. The armature should spin by hand without any drag with the brushes removed. Here's a pic of the so called revolutionary cordless motor. The copper tabs on either sides by the pivots make a contact with the handle, hence there's no wire to bend. I took this opertunity to test run mine. I don't have a variable voltage power supply, but I have a pedal off of a singer sewing maching I use to test run them. This one runs really good.
And, a picture of her sexy hind end, because, why not? These things have two brass screws you remove with wicks in them that hold oil for the bushing. I like to wash them with brakeclean, while apart and let them air dry for a few days before putting a few drops of oil on them. That's it for now, I'll be working on the handle afore long.